1. Field of the Invention
The present invention relates generally to apparatus for manufacturing semiconductors, such as integrated circuits obtained by processing silicon wafers, and more particular relates to clips for retaining a semiconductor wafer on a pedestal of associated semiconductor processing apparatus.
2. Discussion of Related Art
Semiconductor conductor wafer processing equipment typically include one or more pedestals, that are generally vertically oriented, upon which semiconductor wafers are secured via specially designed clips to the pedestals. The clips are generally arranged around the circumference of the pedestal, in sufficient number, for securing a semiconductor wafer to the pedestal in such a manner that the clips can be operated to a position out of engagement with the edges or outer circumference of the associated wafer, for either permitting its installation or removal from the pedestal, and to another operative position for contacting typically the top edge of the wafer for safely securing the wafer to the pedestal without chipping or otherwise damaging the semiconductor wafer.
DiNapoli, et al. U.S. Pat. No. 5,183,245 (hereinafter DiNapoli), entitled "SEMI-CONDUCTOR WAFER RETENTION CLIP", shows and describes both a prior art clip (see FIG. 6 hereof), and an improvement to the securement head 91 of the prior clip, in a clip design as shown in FIG. 4 thereof (see FIG. 1 hereof). Although the present inventors believe that DiNapoli shows an improvement relative to prior clips thereto for reducing the amount of contamination to associated semiconductor wafers caused by the retention clips, the contamination problem still persists. Also, its Applicants' understanding that the improved clip design of DiNapoli, while reducing such contamination problems, increased electrical or plasma arcing problems that tend to reduce the yield of semiconductors devices from the semiconductor wafer being processed.
As taught in DiNapoli, the clip heads of the semiconductor wafer retention clips are formed of Lexan.RTM. material, a plastic material. A metal spring is used to spring bias the pedestal clip, and retain the same to a metal base member. Metal screws are used to secure the spring to the clip head thereof. During processing of the associate semiconductor wafer, plasma etching is typically used. Unfortunately, in addition to etching away selected portions of the semiconductor wafer, the plasma also causes etching or decomposition of the plastic material of the plastic clip head of the semiconductor wafer retention clip. Although the improved semiconductor wafer retention clip of DiNapoli eliminated a portion of the plastic material of the clip head, plasma etching of the remaining clip head still occurs, and results in disintegration of the plastic material of the clip head that still presents a contamination problem when some of the material removed from the clip head by the plasma falls onto the surface of the associated semiconductor wafer. This typically occurs at certain times when the clip head moves between positions for retaining the wafer and positions for not engaging the wafer. Another problem that still persists is that the chemical plasma used in the plasma etching process is generated with high voltage radio frequency or energy or electromagnetic fields, typically attaining voltage levels in the range of 2000 volts. The high energy plasma at times causes voltage arcing to surfaces such as presented by the metal screws attached to the metal spring used in the clips.
The present inventors recognize that although the semiconductor wafer retention clip improved design shown in DiNapoli does apparently reduce contamination of the semiconductor wafer from plastic material etched away from the plastic clip, the contamination problem was not eliminated, and continues to reduce the yield of semiconductor integrated circuits, and so forth, obtainable from associated semiconductor wafers after processing. Also, the previously mentioned arcing problem, when it occurs, substantially reduces the yield.